Twisted pair communications cable is used for high frequency signal transmission, typically in plenum areas of buildings. The cable is composed of typically multiple twisted pairs of polymer-insulated conductors, covered by a polymer jacket. In twisted pair data cables, the individual insulated conductors are typically twisted into pairs, and four pairs are cabled together and jacketed to make the cable. Each pair is twisted at a different lay (conventionally measured in inches/turn) to reduce electrical coupling between adjacent twisted pairs (i.e. crosstalk). The twisting together compresses (i.e. crushes) the polymer insulation. The shorter the lay, the tighter the twist and the greater the crush or compression of the polymer insulation (whether foamed or unfoamed). The twisted pairs are typically designed to have 100 ohms impedance. The center to center spacing of the conductors within the pair is a key factor affecting impedance. Therefore, because increased compression brings the conductors closer, additional insulation thickness is needed to maintain the desired impedance as the length of twist becomes shorter. The problem with increasing the amount of polymer insulation used is that there is an increase in cable weight and cable size.
It is thus desirable to have a polymer insulation that maintains the desired impedance and other electrical and mechanical properties without increasing the weight of the insulation material.
The following disclosure may be relevant to various aspects of the present invention and may be briefly summarized as follows: U.S. Pat. No. 5,990,419 to Bogese, II discloses a primary conductor of wire (solid or strands) that are enclosed by a coating of solid insulation with radially outward extending ribs. The insulated ribs of a first insulated conductor are located adjacent to a second insulated conductor in which the outermost end of the first and second insulated conductor ribs abut. The abutting ribs of the first and second insulated conductors define air spaces which are between the ribs and increase the distance between conductors from each other, thereby reducing the capacitance of the cable assembly.